I actually don't think it is a good idea to deny communion to those jerks. It just turns them into martyrs in the media.
I think a much better way to go would be to be VERY vocal about the issue, lay all the cards on the table, and then presume that they have changed their ways if they come to get communion. If it becomes apparent that they haven't then the bishops should continue to be vocal, talking about how such politicians are desecrating the sacrament, etc. and putting their souls in jeapardy.
The only way I think they should be denied communion is if they come up to the priest with a pro-"choice" button on their shirt, or a rainbow sash, etc., making it obvious that they intend to desecrate the sacrament.
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